To generate an especially good heat transfer between a seating face of a storage plate support and a storage plate, during coating with a sputter source in a vacuum installation, the seating face of the storage plate support is slightly annularly convexly arched and the storage plate is clamped in the center as well as on its outer margin by a center mask and an outer mask against the arched seating face. Hereby an especially good heat transfer is attained with very low arching d, whereby the storage plate is treated gently and simultaneously, during the coating process, no layer thickness distribution problems occur through arching that is too large.

The invention relates to a storage plate support as well as to the use of a storage plate support for processing optical storage plates.
Surface treatment of storage plates for information technology today takes place during the production of such plates primarily with processes in vacuum systems. Herein storage plates are treated for magnetic storage techniques as well as optical storage systems. For surface treatment plasma vacuum processes are often employed, for example for etching the surface, activating the surface, cleaning the surface and in particular depositing layers onto the plate. For the coating process often the widely used sputtering process is employed. Particularly advantageously the plates are coated individually in sequence and cyclically in compact installations. The station times are herein in the range of seconds in order to attain high throughputs for economical reasons.
In the case of magnetic storage plates, the plates onto which layers are applied are as a rule comprised of metal or glass, and, in the case of optical storage plates, optical plastics or polymers are preferably used. Especially during the sputtering process, in which a sputter target is sputtered with the aid of a plasma process at a distance of a few centimeters from the plate, the coating of the plate or of the disk in general entails a rather high introduction of heat, in particular since high deposition rates are necessary with the short required station times. The thermal loading is primarily due to electron bombardment, heat radiation, and kinetic as well as condensation and excitation energy of the coating material. In particular with polymer plates or substrates, and especially in the case of thin plates with low heat capacity, this leads to a temperature increase of the plate if this thermal energy is not sufficiently dissipated. In such cases it is possible for the synthetic plate, which typically is comprised of polycarbonate, to be plastically deformed such that it becomes unusable. Maintaining a safe maximum temperature and attaining a uniform temperature distribution over the plate are essential criteria for achieving good storage plate quality.
It is generally known that the heat transfer in a vacuum is very poor. This is especially the case at low temperature differences, for example of  less than 100xc2x0 C., such as should be reached in these applications. One option for cooling the plate comprises allowing the coating process in different process stations to proceed sequentially and to interspace one or several cooling stations in between, which cools the plate between the coatings before reaching maximum temperature. The heat transfer between a cooled face and the back of the plate can herein be improved by means of a heat transfer medium, such as for example helium. Short distances or even the supporting of the faces are herein advantageous and the pressure of the gas is increased up to the mbar range in the cooling station. In addition, attempts have been made to press the plate with the aid of electrostatic attraction against a cooled face and to improve the heat transfer by means of a gas cushion. In the case of flat rigid plate-form substrates or workpieces, attempts were furthermore made to hold these at the margin and to tighten it on a spherical arched surface, wherein also a contact pressure is generated which also makes possible gas cooling on the back side, as has been disclosed for example in U.S. Pat. No. 4,615,755. Apart from an improvement of the heat transfer with the aid of gases, contact materials have also been employed, such as tin foils, elastomers, or even paste-form materials.
Use of separate cooling stations between the process stations require considerable technical effort. Moreover, the cooling time is limited to a fraction of the total process time of the substrate, which, in turn, requires good heat transfer through high thermal conductivity and/or a cooling surface cooled below ambient temperature.
Electrostatic attraction of the substrate is difficult to realize especially in the case of nonconducting substrates and produces contact pressure which are significantly lower than the contact pressure which can be attained with conducting substrates. This could take place through a conducting coating of the substrates on the back side or generation of a minimally necessary conductivity in the substrate through suitable doping. But, in particular in the case of optical discs, this is not desired, since, apart from the higher substrate costs, the optical properties of the substrate can also be unfavorably impaired. Clamping the substrate at the outer margin and stretching it onto a spherical or cylindrical face requires stressing range causes stresses in the substrate material such that it can become plastically deformed. In addition, due to the large stressing range, the surface form of the substrate is changed such that thereby the uniformity of the coating is impaired.
The present invention addresses the problem of eliminating the disadvantages of prior art. In particular, the task of the present invention is to bring a substrate at a predetermined contact pressure into contact with a cooling face, such that the contact pressure is maximally uniformly distributed over the surface and uniform thermal contact occurs. The substrate is herein subjected to minimum flexing stress without the substrate undergoing plastic deformation and while making possible uniform coating.
This task is solved according to the invention through the characteristics of claim 1. Further advantageous embodiments are contained in the dependent patent claims. According to the invention a storage plate support is developed in the region of the seating face for the storage plate such that it is annularly convexly arched such that the storage plate can be clamped in the center as well as also at its outer margin over this annularly convexly developed seating face. Thereby the storage plate assumes the slightly arched, convex form of the seating face after it is fastened. Thereby that this type of storage plate has an opening in the center, these plates can be tightened in this manner in the center as well as also along the outer margin over a mounting which is simultaneously developed as a mask to prevent coating on these sites. This annular, toroidal arching of the plate leads to a significantly more rigid disposition at higher and more uniformly distributed contact pressures over the face as has been possible within prior art and this takes place simultaneously with substantially lower required deflection. The plate is hereby less deformed and simultaneously this low deformation no longer has a negative effect onto the layer thickness distribution of the coating.
The convex flexure line does not necessarily need to be spherical. Due to the temperature gradient between front and back side of the substrate during the coating, this can for example also be taken into consideration in the form of the contact face through additional curvature forms. In particular due to the simple and defined maintainable geometry, the convexity is thus uniquely determined by the constraint conditions on the substrate, such as outer and inner seating, respective clamping condition, pressure forces onto the back side and thermal flexing forces due to temperature gradients in the substrate. A person skilled in the art can now apply known methods for calculating the necessary deformation, such as analytical or finite element calculation methods.
Apart from the form of the seating face, thermal contact can additionally be further improved through a gas cushion, preferably with a gas of high thermal conduction, such as for example helium. The maximum gas pressure should be below the contact pressure. Moreover, ductile metal foils, for example foils comprising tin, or elastomeric films can additionally be advantageously combined with the invention. The storage plate support can be employed for heating as well as also for cooling if it is correspondingly equipped with means for this purpose. But the configuration is advantageously employed for cooling optical storage plates. For this purpose the storage plate support is developed for example as a copper structure, which includes cooling channels through which flows a cooling medium such as cooling water.
The configuration is especially suited for use of optical storage plates comprised of polymer material, in particular of polycarbonate. Such storage plates are known under the term compact discs (CD) and digital versatile disc (DVD). It is understood that this also subsumes all modified types such as CD-R, CD-RW, DVD-R, DVDxe2x88x92RW, DVD+RW, DVD-RAM, which means all writable and rewritable implementations. In particular DVDs are especially problematic in handling, since DVDs are produced from substrates approximately half as thick as CDs, namely in the range of thickness of 0.6 mm. At these thicknesses, thermal effects are especially critical.
The invention will be described in conjunction with a typical embodiment example for cooling rewritable DVDs. For the manufacture of such DVDs typically two substrates comprised of polycarbonate are produced, which are 0.6 mm thick and have a diameter of 120 mm, and subsequently bonded together. The circular substrates have an inner hole in the center with an inner hole diameter of 15 mm. Coating takes place in a vacuum sputter installation, with the layer system comprising for example the following layers: first on the substrate side a layer of ZnS:SiO2, then the optical recording layer, a so-called phase change material, such as for example TeGeSb, then a ZnS:SiO2 layer and lastly an at least partially reflecting aluminum layer with a layer thickness in the range of 100 to 300 nm. The coating of such layer systems typically takes place in a multichamber installation with, for example, six process chambers, with a total coating time of 30 to 60 s. The heat introduction during the coating is approximately 10 J/cm2 or around 1 kJ for the entire disc. The maximum temperature of the disc should be kept as low as possible in order to avoid plastic deformations of the disc; the disc temperature should ideally be lower than 50xc2x0 C. During the coating the outer mask as well as the inner mask, as a rule, according to prior art are held magnetically on a flat substrate support. During coating, the front side of the disc is heated by the heat flow by around 10xc2x0 C. relative to the back side, which causes the disk to arch up by about 0.3 mm. Thereby the thermal contact to the substrate support is virtually interrupted. The disc is only cooled right at the outside and right at the inside and becomes impermissibly deformed through the nonuniform temperature loading in the plastic range even if the flat storage plate support is comprised of a good heat-conducting material, such as copper, and is well cooled.
In comparison, the implementation according to the invention has the convexly formed and toroidally arched seating face of the storage plate support. The storage plate support is preferably also a copper structure and is cooled in the same manner as the previously described support. In this example the arching of the support is 1 mm. The same DVD plate was worked under the same conditions for the remainder. The arching of 1 mm leads to a contact pressure of approximately 15 mbar in the case of a cold storage plate. The tensile and compressive stresses occurring herein in the disc are maximally 7 MPa, according to the definition after van Mises (Dubbel, Taschenbuch fxc3xcr Maschinenbau, 14th Edition, p. 228) of comparison stresses calculated with the finite elements method. During the coating the front side of the disc is heated by the heat flow relative to the back side by about 10xc2x0 C., which slightly reduces the contact pressure and thus also the plate stresses. For comparison, the deflection will be given in the case of a disc clamped only at the outer margin. To attain a contact pressure of 15 mbar, herein a deflection of 3 mm must be generated, with 1 mm occurring through the thermal loading alone. The stronger arching also leads to a greater layer thickness deviation in the coating than in the type of clamping on the inside and the outside according to the invention.
Without cooling the disc temperature increases by around 100xc2x0 C., and after cooling it becomes unacceptably warped. With a flat storage plate support the disc temperature during the unloading from the installation is approximately 85xc2x0 C. A certain cooling probably takes place, and a heat transfer coefficient between disc and support of around 50 W/K/m2 can be estimated. With the storage plate support according to the invention the disc temperature after coating is approximately 45xc2x0 C. Consequently the temperature increase is here only approximately 25xc2x0 C. relative to ambient temperature. With the storage plate support according to the invention, consequently, a heat transfer coefficient of approximately 150 W/K/m2 is attained. Surprisingly, it could also be found that through the outgassing of substrates of synthetic materials a type of gas cushion is generated between the back side of the plate and the storage plate support seating face, which makes possible an additional improvement of the heat transfer.
Due to the annularly convexly shaped implementation of the seating face of the storage plate support and due to the mounting of the plate at the outer margin and inner margin, a uniform contact pressure is generated between plate and storage plate support, which is maintained even under thermal loading through coating with sputter sources. Hereby a sufficient cooling of the storage plate via the storage plate support is made possible. The uniform contact pressure also produces uniform cooling of the storage plate and therewith avoids excessive thermal, radial and tangential stresses, which would cause the storage plate to become plastically deformed after cooling. The arching of the storage plate support according to the invention is so minimal that it only deviates slightly from a flat seating face. Hereby not only the unacceptable distortion of the storage plate is avoided, the unfavorable effect onto the layer thickness distribution during the sputtering process is also largely avoided.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure and are entirely based on the Swiss priority application 2001 1945/01 filed Oct. 23, 2001. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.

Storage plate support for receiving disk-shaped storage plates


Devices and methods for selectively emplacing a wear bushing in a wellhead housing and removing it therefrom. A drill string-mounted running tool is used to selectively engage the wear bushing during emplacement and removal. The wear bushing need not be removed each time the drill string is tripped into or out of the well. In addition, the drill string may continue to be lowered after the wear bushing is landed since the running tools described can easily pass through the bushing.

1. Field of the Invention
The present invention relates to devices and methods for running a wear bushing into and retrieving a wear bushing from a well.
2. Description of the Related Art
Wear bushings, or wear sleeves, are used to protect the interior of the wellhead during drilling. A typical wear bushing is landed in the wellhead housing before the bit is run into the well. The wear bushing is then removed after drilling and before the well is lined with casing. Traditionally, separate trips with a running tool and, later, a retrieval tool were required to emplace and them retrieve the wear bushing. An example of this type of system is described in U.S. Pat. No. 5,762,136 issued to Oswald. Unfortunately, the extra trips for the running tool are costly and time consuming.
There are a few systems known that have attempted to couple the operations of running and retrieving the wear bushing with those of running and retrieving the drill bit from the wellbore. Unfortunately, these systems do not, in practice, provide workable solution.
U.S. Pat. No. 3,247,914 issued to Slack describes a technique wherein a wear bushing protector loosely surrounds the drilling string. The diameter of the drill bit is larger than the inside diameter of the protector allowing the protector to be carried top the drill bit for loose placement into and removal from the wellhead housing. However, this sort of arrangement is impractical today since it is preferred to pass a drill bit through the wear bushing during use, and the diameter of drill bits used is smaller than the interior of the wear bushing.
U.S. Pat. No. 3,489,214 issued to Phipps describes a system wherein a wear sleeve also located on a drill collar above the drill bit for placement in a wellhead. The wear sleeve is provided with interior J-slots that can be engaged by pins on the drill collar. If it is desired to retrieve the wear sleeve without bringing the drill bit all the way up and out of the hole, a specialized retriever tool is incorporated into the drill string. The wear sleeve can then be retrieved by lowering the retriever tool down to the level of the wear sleeve and engaging the J-slots of the wear sleeve with pins on the retriever tool. While this type of arrangement is effective, it requires the drill string to be broken down in order to incorporate the retriever tool into the drill string. After the wear sleeve is removed from the well, the drill string must be broken down a second time to remove the wear sleeve and the retriever tool. A further problem with this design is that the downward movement of the drill string is limited by the wear sleeve. The retriever tool cannot pass through the wear sleeve because the outwardly projecting pins and rings prevent passage. If it is desired to advance the drill bit downhole, one must pull the drill string out and break it down to remove the retriever tool.
U.S. Pat. No. 4,625,381 issued to Gravouia, Jr. et al. also describes a system wherein a wear bushing can be retrieved using a retriever section with J-slots. This system suffers from substantially the same drawbacks as the Phipps system
U.S. Pat. No. 4,362,210 issued to Green describes a friction hold wear bushing. A wrench is rotated to cause the specialized wear bushing to selectively engage the casing in a frictional grip.
U.S. Pat. No. 4,995,458 issued to Garbett describes wear bushing retrieval arrangements wherein a latching device is secured to the outside of a length of casing during a late stage of the casing running operation. The latching device engages a groove on the interior of the wear bushing. The wear bushing can then be removed from the wellhead casing by pulling upward on the casing string. It is noted that Garbett""s system involves actually drilling through the wear bushing at the start of drilling.
The prior art arrangements have a number of operational problems. In systems such as those described in Garbett, once the wear bushing has been landed, the drill string cannot be readily moved downwardly further into the wellbore because progress of the retrieval tool becomes blocked by the wear bushing. On the other hand, systems such as those taught in Slack remove the wear bushing every time the bit is removed from the wellbore. This is undesirable. Phipps system requires that the drill string be disassembled to incorporate the retriever tool. Additionally, many prior art techniques do not provide a means for securing the wear bushing to the drill string for running the wear bushing. It would be desirable to have devices and methods that address the problems of the prior art.
Arrangements are described wherein wear bushing can be selectively emplaced in a wellhead housing or removed therefrom. A running tool is used to selectively engage the wear bushing during emplacement and removal. The wear bushing need not be removed each time the drill string is tripped into or out of the well. In addition, the drill string may continue to be lowered after the wear bushing is landed since the running tools described can easily pass through the bushing. Further, the drill string need not be broken down in order to incorporate the running tools.
In a first exemplary embodiment, a running tool is incorporated into the drill string at the outset of drilling operations and provided with a radially expandable C-ring that engages an inner portion of the wear bushing as the drill string is tripped in. Once the wear bushing is landed in the wellhead housing, the C-ring is cammed radially inwardly as the drill string and running tool are disposed further downhole. The drill string and bit may be removed from the well by simply pulling them directly out of the well. If it is desired to remove the wear bushing, such as after a portion of the drilling is completed, this may be accomplished without completely tripping the bit out of the well. The C-ring of the running tool is moved to a radially expanded position by disposing a dart, plug or wiper into the flowbore of the drill string and providing fluid pressure inside the flowbore. The drill string is then moved upwardly to the point that the C-ring engages the wear bushing. Tripping out of the drill string from the well to the point that the running tool is removed will remove the wear bushing as well.
In a second described embodiment, spring-based locking pins that selectively project radially outwardly are used in place of a radially expandable C-ring. The pins initially engage the wear bushing and carry it upon the drill string as the bit is run into the well. After the wear bushing is landed, and the bit disposed lower into the well, the pins are retracted radially and retained in that configuration. As a result, the drill string and bit may be removed from the well without removing the wear bushing. Fluid pressurization within the flowbore of the drill string will cause the pins to expand radially so that the wear bushing may be engaged by the running tool. The wear bushing may then be removed from the well by removing the drill string and running tool from the well.
In a third described embodiment, the drill string is selectively secured to a wear bushing by locking pins that are caused to selectively project radially outwardly from the running tool. The drill string is also secured by a xe2x80x9cweakxe2x80x9d C-ring arrangement to a locking assembly having a set of locking dogs that engage the wellhead. After the wear bushing is seated in the wellhead housing, weight is placed upon the drill string to release the drill string from the locking assembly and the wear bushing.

Wear bushing running and retrieval tools


A portable door lock comprises a jam plate connected through a hinge to a latch plate through a hinge that allows the latch plate to swing from a lock position alongside a door to an unlock position alongside a door jam when the portable door lock is installed in a door jam recess between a door and a door jam so the lock can remain installed yet allow the door to be opened for normal use or locked. A jam plate tongue extends orthogonally from the jam plate adjacent a jam plate hole sized to receive a door latch striker therethrough. Preferably two opposing upper and lower hooks opening in opposite directions swivel on the latch plate on a pivot pin in a plane parallel to the latch plate one hook applicable for a right-hinged door, the other for a left-hinged door. The hooks also may wrap and hook a doorknob shank from above and below. In an alternate embodiment, the hooks may comprise a rigid hook plate with the first and second hooks opening in opposite direction, one useful for left-hinged doors, the other for right-hinged doors.

1. Field of the Invention
This invention relates to portable door locks, and, more specifically, to locking devices adapted to engage a door jam recess plate of a latch door and a doorknob of that door to prevent the door from opening when the striker is withdrawn.
2. Prior Art
It is often desirable to have a locking device supplemental to doorknob locks and lock bolts and latch chains and the like. These built-in locking mechanisms may serve to protect an occupant from most intruders, but they may not be sufficient to protect against intruders that have keys, including hotel workers with master keys but also including those that might obtain copies of keys surreptitiously and even those that are adept at picking locks. For enhanced security against such circumstances, travelers seeking protection beyond the provided locking mechanisms must bring with them their own locking device.
To be practical, the device must be reasonably small and lightweight, suitable for traveling. It must be easily and quickly applied and removable so the occupant may enter and exit his or her room without undue delay or trouble or the occupant will be tempted to leave the supplementary lock disengaged or uninstalled. It must be of nominal cost in order to be available to the occasional traveler. And it should engage the door jam so it continues to protect when the door lock striker or bolt has been withdrawn.
Portable locking devices are known in the art. Bey in U.S. Pat. No. 4,022,503 discloses a chain for looping around a doorknob shank and a hook on the chain for engaging a door striker plate. Roberts in U.S. Pat. No. 4,135,748 discloses a rod with a first hook on one end and a chain on the other with a second hook on the chain end for engaging chain links when looped around a doorknob shank. And David in U.S. Pat. No. 5,360,245 discloses an insert member with a portion that engages the door jam recess and a latching member, disconnectable from the insert member that swings over a doorknob shank at a latching member recess.
These various forms of portable door locks serve their function well, however, the portion of the Bey and the Roberts devices that engages the door jam recess may fall out, and all three may interfere with the door striker in the door jam recess or strike plate. Perhaps more importantly, the questionable strength of the lock inherent in their designs suggests a need for a stronger lock able to withstand forceful attempt to open the door. Further, when a force applied when attempting to open a locked door is focused at an area smaller that a door striker, the pressure caused by the same force is greatly increased with the result that where door jam might be designed to withstand such a force, when focused to a smaller area through a hook as disclosed in the prior art, the increased pressure of the force is more likely to cause the door jam to fail.
An object of the present invention therefore is to present a portable door lock with increased strength of materials and design to better resist entry by force that might break locks of previous designs. Another object is that the lock be stable in the door jam, so when the door is opened for normal use, the lock does not fall out of the door jam recess or strike plate, allowing the occupant normal use of the door until locking it while the door lock remains in place. A further object is that the door lock be comparatively lightweight and small for ease of transport by a traveler. A still further object is that force of opening the door applied through the door striker to the door jam recess or striker plate continue to be so applied by means of the portable lock when the striker is removed. A final object is that the door lock be applicable to doors hinged on either the right or the left.
These objects are achieved in a portable lock that employs a jam plate with a tongue normal to the plate that engages a door jam recess or a strike plate recess. A hole in the jam plate adjacent the tongue receives a door latch striker passing through and into the door jam recess.
A latch plate connects to the jam plate at a hinge so when the jam plate is installed in the door jam, the latch plate can hinge away from the door so the door can open or alongside the door for locking. A first latching hook, connected on a pivot pin at a latch plate distal end, allows the latching hook to swivel in a plane parallel to the latch plate. With the supplemental door lock installed in a door jam recess, the hook then wraps over the doorknob shank to secure the door. If one attempts to open the door with the hook wrapped over the doorknob, the door pushes against the hook around the doorknob shank and pulls the tongue against the door jam striker recess. Thus, though the door striker may be withdrawn from the recess, the portable door lock communicates the force normally communicated over the face of the striker to the same door jam recess or strike plate force normally communicated the face of the insert plate tongue. Thus, if the door jam with the striker in the recess would withstand the applied force against the door, so would the door jam with the portable door lock of the present invention.
A second latching hook also connected on the pivot pin with the first latching hook opposes the first latching hook. That is, the first latching hook opens down and the second latching opens up toward the first latching hook. In use then, the first latching hook wraps over the doorknob and hooks the shank from above the doorknob, and the second latching hook wraps under the doorknob and hooks the shank from under the doorknob to double the strength of the lock. With full revolution pivot capability around the pivot pin, the portable lock applies equally well to left-hinged doors and right-hinged doors.
In an alternative embodiment, the latching hook comprises a single hook plate pivoting on the pivot pin. The hook plate comprises a first hook opening upward and a second hook opening downward. Thus, depending on whether the door is right-hinged or left-hinged, the portable lock employs either the first hook or the second hook on the latch plate to wrap over the doorknob shank.
Necessarily, the jam plate must be thin to fit between a door and a door jam, and, to withstand an opening force against the door, the jam plate is broad to enhance lock strength by distributing force against the door across the breadth of the plate. Similarly, the jam plate tongue is also broad, comparable to a door striker, and sized to fit in a door jam recess or strike plate recess. Because it must share the recess with the striker, it also must be thin but with a broad area to distribute an opening force over the jam recess. Given that the door jam is designed to withstand a normal opening force with the striker is locked in the jam recess by distributing the opening force through the striker over jam recess side, when the striker is withdrawn, the portable lock ideally distributes the opening force over the same jam recess side, thus maintaining the same pressure against the door jam . Thus, the jam plate tongue though thin to fit in the recess with the striker, presents a broad contact area to the jam recess comparable to the door striker to maintain a similar opening pressure distributed to the door jam by the tongue.
The lock jam plate is typically at least as broad as the plate tongue to transmit the opening force from the latch plate to the tongue without breaking. Similarly, the latch plate is of similar breadth as the tongue as also are the hinge portions from each plate of total breadth approximately that of the tongue. The line of joinder of the tongue to the jam plate is the full height of the tongue, similar to the height of the door striker, which is typically obtained by cutting three sides of a rectangle through the jam plate and folding the rectangle from the jam plate on the rectangle fourth side.
Conveniently, the supplementary portable door lock is foldable on its hinge between a lock position alongside a door and an open position away from the door and alongside the door jam. In that open position, the weight of the latch plate and hooks pull the jam plate tongue against the door jam recess. Thus, the portable door lock remains installed in the door jam recess but is easily removed by simply withdrawing the tongue from the door jam recess.
Clearly, the portable door lock is applicable to either a door hinged on its left or its right side. The portable door lock is simply inverted from one application to the other.


A wetness indicating hot melt adhesive composition comprising a pH adjusting component and an indicating agent which is capable of changing color in response to changes in pH. The adhesive composition may comprise 20 to 80% by weight of a sulfonated polyester, 3 to 30% by weight of an acidic plasticizer and 0.05 to 3% by weight of an indicator.

Hot melt adhesives, 100% solids materials, which are applied to a substrate when molten and cooled to harden the adhesive layer, are used commercially for a wide variety of applications. The major advantage of hot melt adhesive systems is the lack of a carrier fluid which eliminates the need for drying the adhesive film once it is applied to the substrate. This elimination of the drying step overcomes hazards associated with solvent usage and also allows for faster production line speeds and lower transportation costs.
For various applications, it is also desired that some hot melt adhesives be hydrophilic, i.e., be water-soluble, water-sensitive or water-activated. Such hydrophilic adhesives find use, for example, in moisture activated envelope adhesives and in the construction of flushable disposable products including diapers and sanitary napkins where they promote the disintegration of the disposable article in water.
Hot melt adhesives have historically been based on petroleum derived polymers such as polyethylene, ethylene-vinyl acetate, styrenic block copolymers and polypropylene. Water sensitive hot melts have also been prepared from vinyl pyrrolidone polymers including vinyl acetate/vinyl pyrrolidone copolymers. All these adhesive compositions are further tackified, plasticized and/or reinforced with a variety of resins, oils and/or waxes which are derived from both petroleum and naturally occurring feedstocks such as wood, gum and tall oil rosin and terpenes.
In the production of disposable articles, hot melt adhesives are typically extruded at elevated temperatures (about 250xc2x0 F. to 350xc2x0 F.) directly onto a work piece, typically a polyethylene or polypropylene film, a nonwoven fabric, an absorbent material, a tissue, or a film which can then be bonded to another nonwoven fabric, absorbent material, tissue, or film using the hot melt adhesive. Application of the adhesive may be extruded by fine line, multi-dot, multi-line methods or spray techniques. The hot melt adhesive is used to laminate layers or attach elastic, particularly for waist or leg band closures for disposable diapers.
In such disposable products, it is desirable to know if the product has become wet with water or urine. For example, it may not be readily apparent that a diaper has become wet due to the plastic coating or water proof panty worn over the diaper.
Accordingly, the present invention is directed to a hot melt adhesive composition which is capable of indicating the presence of water or urine therein and to disposable products comprising such adhesives. Specifically, the hot melt adhesives of the present invention change color in response to water or urine.
The hot melt adhesives of the present invention comprise a pH adjusting component and an indicating agent which is capable of changing color in response to changes in pH.
The adhesives of the present invention comprise a pH adjusting component and an indicating agent which is capable of changing color in response to changes in pH.
The indicating agent is a component which is capable of changing color in response to changes in pH. Acid-base indicators are preferred because they change color rapidly. The most preferred indicating agents are those which change to a bright, vivid color. The acid-base indicators for use herein are those which change color at a pH in the range of about 3 to 7, such as Ethyl Red, Bromophenol Blue (made by Eastman Kodak), Bromocresol Green mixed with Bromophenol Blue, or Bromophenol Blue. Most preferred is Bromocresol Green which changes color in the range pH 3.8 to 5.4.
The indicating agent is used in an amount effective to provide the composition with a readily visible color when the composition exposed to water or urine; generally about 0.05 to 0.1 weight percent indicator, based on the weight of the composition. Preferably, the indicating agent is present in amounts of 0.005 to 3% by weight of the adhesive composition.
The adhesives of the present invention also comprise a pH adjusting agent which is an acidic or basic component which changes the pH of the hot melt adhesive. Preferred are acidic plasticizers which have an acidic functional end group, such as a carboxylic acid. Examples of such acidic plasticizers include isostearic acid, azelaic acid, stearic acid, oleic acid, linoleic acid, ricinoleic acid and dimer acid. Isostearic acid is preferred.
The acid plasticizer is used to render the resulting adhesive acidic. As used herein, acidic is defined as a pH less than the indicating range of the indicating agent. The adhesives described herein, without the acidic plasticizer, are of a pH such that the addition of Bromocresol Green (or any indicating agent) to the adhesive causes the indicator to change. Therefore, it was found in accordance with the present invention, that the addition of an acidic plasticizer adjusts the pH of the adhesive to below the activation range of the indicating agent, preventing the indicating agent from changing color unless exposed to a substance that will raise the pH, such as water or urine, as will be described below.
Specifically, the addition of urine, which has a pH is the range 5.8 to 7.4, or the addition of water with a pH of 7, to the adhesive, causes the pH of the adhesive to increase, passing through the indicator range, causing a color change signaling that the adhesive is wet with water or urine. The pH range of urine is disclosed in J. L. Hammone, et al. TAPPI Int. Dissolving Pulps Conf. (Geneva) Proc.: 247-264 (Mar. 24-27, 1987).
Any indicating agent capable of changing color in response to a change in pH may be used. Therefore when formulating an adhesive in accordance with the present invention, the acidic plasticizer and indicating agent are chosen so that the pH of the adhesive is such that when urine or water are added, the pH changes in such a way that the indicator is activated.
The pH adjusting agent and indicating agent are formulated into an adhesive composition. Any base polymer for hot melt adhesives may be used such as polyethylene, ethylene-vinyl acetate, styrenic block copolymers, polypropylene, and vinyl pyrrolidone polymers including vinyl acetate/vinyl pyrrolidone copolymers. Preferably the base polymer is a sulfonated polyester. In this embodiment, the present invention is directed to hot melt adhesive compositions comprising (a) 20 to 80% by weight of a sulfonated polyester; (b) 3 to 30% by weight of a pH adjusting agent, particularly an acidic plasticizer; and (c) to 0.05 to 3% by weight of an indicating agent capable of changing color in response to changes in pH.
The major component of the adhesive of the invention, present in an amount of 20 to 80% by weight of the adhesive, is a sulfonated polyester condensation polymer comprising the reaction product of:
(a) at least one difunctional dicarboxylic acid or corresponding methyl ester which is not a sulphomonomer;
(b) 2 to 25 mole percent of at least one sulphomonomer containing at least one metallic sulfonate group or nitrogen-containing non-metallic sulfonate group attached to an aromatic or cycloaliphatic nucleus and at least one functional group selected from the group consisting of hydroxyl, carboxyl, and amino;
(c) at least one difunctional reactant selected from a glycol or a mixture of a glycol and diamine having two xe2x80x94NRH groups, the glycol containing two xe2x80x94C(R1)2xe2x80x94OH groups wherein R in the reactant is hydrogen or an alkyl group of 1 to 6 carbon atoms, and R1 in the reactant is a hydrogen atom, an alkyl of 1 to 5 carbon atoms, or an aryl group of 6 to 10 carbons atoms;
(d) 0 to 40 mole percent of a difunctional reactant selected from hydroxycarboxylic acids having one xe2x80x94C(R)2xe2x80x94OH group, aminocarboxylic acids having one xe2x80x94NRH group, amino-alcohols having one xe2x80x94C(R)2xe2x80x94OH group and one xe2x80x94NRH group, or mixtures of said difunctional reactants wherein R in the reactant is hydrogen or an alkyl group of 1 to 6 carbon atoms; and
(e) 0 to 40 mole percent of a multifunctional reactant containing at least three functional groups selected from hydroxyl, carboxyl, and mixtures thereof wherein at least a portion of the multifunctional reactant contains at least three hydroxyl groups, wherein all stated mole percentages are based on the total of all acid, hydroxyl and amino group containing reactants being equal to 200 mole percent, and wherein the polymer contains proportions of acid-group containing reactants (100 mole percent acid) to hydroxy- and amino-group containing reactants (100 mole percent base) such that the value of (equivalents) EQ (base) divided by (equivalents) EQ (acid) is between 0.5 and 2.
The difunctional acid or ester reactant of (a) of the composition of the present invention is preferably substantially aliphatic in nature and may be an acid selected from the group consisting of oxalic; malonic; dimethylmalonic; succinic; glutaric; adipic; trimethyladipic; pimelic; pivalic; fumaric; maleic; dodecanoic; 2,2-dimethylglutaric; azelaic; sebacic; 1,3-cyclopentane-dicarboxylic; 1,2-cyclohexanedicarboxylic; 1,3-cyclohexane dicarboxylic; 1,4-cyclo-hexanedicarboxylic; phthalic; terephthalic; isophthalic; 2,5-norbornane-dicarboxylic; 1,3-naphthalic; diphenic; 4,4xe2x80x2-oxydibenzoic; diglycolic; thiodipropionic; 4,4xe2x80x2-sulfonyldibenzoic; and 2,5-naphthalenedicarboxylic acids and esters thereof and mixtures thereof. The difunctional dicarboxylic acid or ester reactant of (a) is preferably selected from the group of acids consisting of isophthalic acid, terephthalic acid, phthalic anhydride (acid), adipic acid, pivalic acid, dodecanedioic acid, sebacic acid, azelaic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexane-dicarboxylic acid, maleic anhydride, fumaric acid, succinic anhydride (acid), 2,6-naphthalenedicarboxylic acid, and glutaric acid and esters thereof and mixtures thereof. The more preferred difunctional dicarboxylic acid reactants of (a) are selected from the group consisting of isophthalic acid, adipic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid and mixtures thereof with 1,4-cyclohexanedicarboxylic acid being most preferred.
The sulphomonomer reactant of (b) is preferably selected from the group consisting of difunctional monomers containing a xe2x80x94SO3M group attached to a nucleus selected from the group consisting of benzene, naphthalene, anthracene, diphenyl, oxydiphenyl, sulfonyldiphenyl, and methylenediphenyl, wherein M is Na+, Li+, Mg++, Ca++, Fe++, and Fe+++. The more preferred sulfomonomer reactant of (b) is selected from the group consisting of diols an diol adducts of multifunctional reactant containing at least three hydroxyl groups and a monocarboxylic acid sulfomonomer containing at least one metallic sulfonate group or nitrogen-containing non-metallic sulfonate group attached to an aromatic or cyclo-aliphatic nucleus. Alternatively, a more preferred group of sulfomonomers include 5-sodiosulfoisophthalic acid, dimethyl 5-sodiosulfoisophthalate, 5-lithiosulfoisphthalic acid, and bis(2-hydroxyethyl)-5-sodiosulfoisophthalate; with the 5-sodiosulfoisophthalic acid or dimethyl 5-sodiosulfoisophthalate being most preferred.
The difunctional reactant of (c) is preferably a diol selected from the group consisting of ethylene glycol; propylene glycol, 1,3-propanediol, 2-methyl-1,3-propanediol, 2,4-dimethyl-2-ethyl-hexane-1,3-diol, 2,2-dimethyl-1,3-propanediol (neopentyl glycol), 2-ethyl-2-butyl-1,3-propanediol (neopentyl glycol), 2-ethyl-2-butyl-1,3-propanediol, 2-ethyl-2-isobutyl-1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethyl-1,6-hexanediol, thiodiethanol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, p-xylylenediol,diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, hexaethylene glycol, heptaethylene glycol, octaethylene glycol, nonaethylene glycol, decaethylene glycols, 2,2,4-trimethyl-1-1,3-pentanediol, hydroxypivalyl hydroxypivalate, dipropylene glycol, 1,10-decanediol, hydrogenated bisphenol A, and mixtures thereof. The difunctional reactant of (c) is more preferably selected from the group consisting of diethylene glycol; neopentyl glycol, cyclohexanedimethanol, 2-ethyl-2-butyl-1,3-propanediol, 2,2,4-trimethyl-1,3-pentanediol, hydroxypivalyl hydroxypivalate, and 2-methyl-1,3-propanediol, with diethylene glycol, neopentyl glycol, and cyclohexanedimethanol being most preferred.
Advantageous difunctional components which are aminoalcohols include aromatic, aliphatic, heterocyclic and other types as in regard to component (d). Specific examples include 5-aminomethyl-cyclohexanemethanol; 5-amino-2-ethyl-pentanol-1, 2-(4-b-hydroxyethoxy-phenyl)-1-aminoethane, 3-amino-2,2-dimethylpropanol, hydroxyethylamine, etc. Generally these aminoalcohols contain from 2 to 20 carbon atoms, one xe2x80x94NRH group and one xe2x80x94C(R)2xe2x80x94OH group.
Advantageous difunctional monomer components which are aminocarboxylic acids include aromatic aliphatic, heterocylic, and other types as in regard to component (d) and include lactams. Specific examples include 6-aminocaproic acid, its lactam known as caprolactam, omega-aminoundecanoic acid, 3-amino-2-dimethylpropionic acid, 4-(b-aminoethyl)-benzoic acid, 2-(b-aminopropoxy) benzoic acid, 4-aminomethlcyclohexanecarboxylic acid, 2-(b-aminopropoxy) cyclohexanecarboxylic acid, etc. Generally these compounds contain from 2 to 20 carbon atoms.
Advantageous examples of difunctional monomer component (d) which are diamines include ethylene-diamine; hexamethylenediamine; 2,2,4-trimethylhexamethylenediamine; 4-oxaheptane-1,7-diamine; 4,7-dioxadecane-1,10-diamine; 1,4-cyclohexanebismethylamine; 1,3-cycloheptamethylene-diamine; dodecamethylenediamine, etc.
Reactant (e), when used, preferably contains 3 to 6 hydroxyl and/or carboxyl groups; more preferred is trimethylolpropane (TMP), trimethylolethane (TME), glycerine, pentaerythritol, arytritol, threitol, dipentaerythritol, sorbitol, trimellitic anhydride, pyromellitic dianhydride, or dimethylolpropionic acid, with TMP being most preferred. It is preferred that reactant (e) be present in a minor amount up to 40 mole percent, more preferred 0 to 20 mole percent.
The polyester composition used as a component of the hot melt adhesives of the present invention preferably comprises 60 to 100 mole percent of (a), 4 to 20 mole percent of (b), 80 to 100 mole percent of (c), 0 to 10 mole percent of (d), and 0 to 20 mole percent of (e).
In other more preferred embodiments of the invention the polyester comprises 60 to 100 mole percent of 1,4-cyclohexanedicarboxylic acid; 4 to 20 mole percent of 5-sodiosulfoisophthalic acid or dimethyl 5-sodiosulfoisophthalate; and 80 to 100 mole percent of diethylene glycol, neopentyl glycol or cyclohexanedimethanol.
The preparation of the polyesters used herein is generally described, for example, in U.S. Pat. Nos. 4,910,292, 4,973,656, and 4,990,593.
The preferred polycondensation reactant conditions for the preparation of the polyester are at a temperature of 150 to 230xc2x0 C. in the presence of a catalyst. The catalyst for the polycondensation reaction is preferably an acid catalyst more preferably an organo-metallic compound, such as a tin or titanium containing compound. Suitable examples of the acid catalyst include dibutyltinoxide, stannous oxalate, titaniumtetraisopropoxide, butylstannoic acid, and p-toluenesulfonic acid, with butylstannoic acid being most preferred. A preferred butylstannoic acid catalytic amount is 0 to 0.5 weight percent, based on the total weight of reactants, preferably 0.01 to 0.2 weight percent, with 0.1 weight percent being most preferred.
The viscosity of the polyester is preferably between 1000 cP and 1,000,000 cP at 350xc2x0 F., most preferably between 5000 and 60,000 cP. Viscosity is measured in a Brookfield viscometer using a #27 spindle. Viscosity is generally related to molecular weight with higher viscosities corresponding to higher molecular weights.
The adhesive compositions of the present invention may also comprise additional optional components such as polar nonionic, cationic and anionic plasticizers; tackifiers; crystalline materials; and stabilizers.
Depending on the end-use application, various compatible nonionic liquid plasticizers or extending oils may optionally be present in the composition. Preferred compatible plasticizers are non-crystalline in nature and include polar liquid plasticizers including phthalate plasticizers such as dioctyl phthalate and butyl benzyl phthalate (e.g., SANTICIZER 160 from Monsanto); liquid polyesters (non-crystalline) such as DYNACOL 720 from Hxc3xcls and the liquid polymeric plasticizer available from C. P. Hall; benzoate plasticizers such as 1,4-cyclohexane dimethanol dibenzoate (e.g., BENZOFLEX 352 available commercially from Velsicol), diethylene glycol/dipropylene glycol dibenzoate (e.g., BENZOFLEX 50 from Velsicol) and diethylene glycol dibenzoate where the mole fraction of hydroxyl groups which have been esterified ranges from 0.5 to 0.95 (e.g., BENZOFLEX 245 HIGH HYDROXYL also from Velsicol); phosphate plasticizers such as t-butylphenyl diphenyl phosphate (e.g., SANTICIZER 154 available commercially from Monsanto); poly(ethylene glycol) with molecular weight below about 1000 and derivatives of poly(ethylene glycol) (e.g., PYCAL 94, the phenyl ether of PEG, available commercially from ICI);
ethoxylated bis phenol A (e.g., MACOL 206 EM from PPG Industries); dinonyl phenol ethyoxylates (e.g., SURFONIC DNP 100 from Huntsman Chemical Corp.); liquid rosin derivatives having Ring and Ball melting points below about 60xc2x0 C. such as the methyl ester of hydrogenated rosin (e.g., HERCOLYN D from Hercules); as well as vegetable and animal oils such as glycerol esters of fatty acids and polymerization products thereof. Particularly preferred plasticizer include phenyl ether of polyethylene-glycol; butyl benzyl phthalate; benzoates such as 1,4-cyclohexane dimethanol dibenzoate, diethylene glycol/dipropylene glycol dibenzoate, and diethylene glycol dibenzoate where the mole fraction of hydroxyl groups which have been esterified ranges from 0.5 to 0.95. These plasticizers are also polar in chemical composition and show improved compatibility over plasticizers which are not polar such as Mineral Oil.
Examples of cationic plasticizers include the fatty amine quaternary ammonium salts, such as ATLAS G-265 with HLB of 33, available from ICI; and ATLAS-G-3634A an imidazoline quaternary ammonium salt, also available from ICI.
Anionic plasticizers suitable for use herein are available in either solid or liquid form. When present, the adhesive composition will comprise 1 to 30% of anionic plasticizers. Examples of anionic plasticizers include the sulfosuccinate salts, such as sodium dioctyl sulfosuccinate, a solid plasticizer available under the tradename CYTEC OT-100 from Cytec Industries; sulfated fatty acids such as AHCOWET RS from ICI; and EMULSIFIER K-30, a solid alkane sulfonate available from Bayer Inc. Preferred is EMULSIFIER K-30. It has been found, in accordance with the present invention, that the anionic plasticizer will accelerate the color change of the indicating agent.
The compatible tackifying resins useful in the adhesive compositions are generally polar in nature and have a Ring and Ball softening point greater than 60xc2x0 C. and include rosin and rosin derivatives, pure phenolic resins, and the like. More particularly, the useful tackifying resins include any compatible resins or mixtures thereof such as (1) natural and modified rosins such, for example, as gum rosin, wood rosin, tall oil rosin, distilled rosin, hydrogenated rosin, dimerized rosin, and polymerized rosin; (2) rosin esters such as glycerol and pentaerythritol esters of natural and modified rosins, such, for example as the glycerol ester of pale, wood rosin, the glycerol ester of hydrogenated rosin, the glycerol ester of polymerized rosin, the pentaerythritol ester of hydrogenated rosin, and the phenolic-modified pentaerythritol ester of rosin; and (3) phenolic modified xcex1-methyl styrene resins as well as the hydrogenated derivatives thereof. Mixtures of two or more of the above described tackifying resins, as well as blends of the above resins with small amounts of (e.g., less than about 20% of the adhesive) less compatible resins may be utilized for some formulations.
Representative polar tackifiers include ionic materials such as FORAL NC available from Hercules; non-ionic materials such as FORAL AX also from Hercules; alpha methyl styrene phenolics such as URATAK 68520 from DSM Resins, and rosin esters such as UNITAC R100L available from Union Camp. The preferred tackifier for use herein is FORAL NC.
Another tackifier is sucrose benzoate which is particularly useful due to its biodegradable and compostable character. Sucrose benzoate is preferably utilized in its alcohol soluble form wherein the sucrose is partially esterified. This grade is a light colored, clear non-crystalline solid with a softening point of about 95xc2x0 C. Alternatively, the non-alcohol organic soluble grade, a water-clear, non-crystalline flake solid having a softening point of 98xc2x0 C. may also be used. Both grades are available commercially from Veliscol Chemical Corporation.
High polarity hydroxyl-containing tackifiers are most preferred. Among these are styrene allyl alcohol copolymers available from ARCO Chemical under the tradename SAA-100, and orthophthalate neopentyl glycol polyester polyol available from Stepan under the tradename Stepanol PN-110.
Additionally, small amounts (i.e., less than 20 percent by weight) of non-polar tackifiers may be used in combination with the previously described tackifiers. Typical of this class of non-polar tackifiers are the aromatic/aliphatics such as ECR-149B from Exxon Chemical; aromatics such as KRISTALEX 3085 from Hercules; aliphatic hydrocarbons such as WINGTAC 95 from Goodyear; and cyclic aliphatics such as EASTOTAC H-100 from Eastman Chemical.
While the tackifier may comprise up to about 50% of the adhesive, it is generally used in amounts of about 0 to 35% by weight.
The adhesives of the invention may also comprise at least one crystalline wax material selected from the group consisting of a compatible crystalline wax diluent and a crystalline thermoplastic polymer. The crystalline wax materials are employed at levels of about 5 to 40% by weight by weight to reduce the melt viscosity while improving heat resistance. The waxes used must be highly polar, containing xe2x89xa73xc3x9710xe2x88x923 equiv/g of polar groups and at least one group per molecule and with a molecular weight below 500 g/mole. Higher concentrations of polar groups are necessary for higher molecular weight waxes. These polar groups include hydroxyl, amide (primary, secondary, and tertiary), sulfone, phosphate esters, sulfonamide, carbonate, urea, amine, urethane, carboxylic acid; and carboxylate salts, ureas, and sulfonate salts.
Suitable crystalline polar waxes include 12-hydroxystearamide, N-(2-hydroxy ethyl) 12-hydroxystearamide (PARICIN 220 from CasChem), stearamide (KEMAMIDE S from Witco), glycerin monostearate, sorbitan monostearate, and 12-hydroxy stearic acid. Also useful in combination with the above are the less polar waxes such as N,Nxe2x80x2-ethylene-bis-stearamide (KEMAMIDE W-40 from Witco), hydrogenated castor oil (castor wax), oxidized synthetic waxes, and functionalized synthetic waxes such as oxidized polyethylene waxes (PETROLITE E-1040).
The adhesives of the invention may comprise a crystalline component which may alternatively be a crystalline hydrophobic thermoplastic polymer present in the adhesive 5 to 60%, preferably 5 to 40%. These polymers are employed in order to impart flexibility, toughness and strength. Suitable crystalline thermoplastic polymers include ethylene vinyl acetate copolymers containing about 12 to 50% vinyl acetate, ethylene acrylic acid, ethylene methyl acrylate and ethylene n-butyl acrylate copolymers as well as polylactide, caprolactone polymers and poly(hydroxy-butyrate/hydroxyvalerate), polyvinyl alcohol, linear saturated polyesters such as DYNAPOL or DYNACOLL polymers from Hxc3xcls, or GRILTEX from EMS-Chemie, poly (ethylene oxide) polyether amide or polyester ether block copolymers available from Atochem (PEBAX) or Hoechst Celanese (RITEFLEX) respectively, and polyamide polymers such as those available from Union Camp (UNIREZ) or Hxc3xcls (VESTAMELT). The polymers added may be amorphous or crystalline, but at least 5% of a crystalline polymer is required to achieve adequate properties.
Preferred among these crystalline polymers are other polyester polymers such as those available from EMS-Chemie, Sumter, S.C., under the tradename GRILTEX, or from Hxc3xcls America, Piscataway, N.J., under the tradenames DYNAPOL and DYNACOLL (lower molecular weight). Also preferred are polyamides such as those available from Union Camp, Wayne, N.J., under the UNIREZ tradename or copolyamides available from Hxc3xcls under the VESTAMELT tradename and also from EMS-Chemie also under the GRILTEX name.
It may also be desirable to incorporate into the hot melt adhesive up to 20% by weight of certain other hydrophilic non-crystalline polymers such as hydroxyethyl cellulose, hydroxypropyl cellulose, polyvinyl methyl ether, polyvinylpyrrolidone, polyethyloxazoline, starch or cellulose esters, particularly the acetates with a degree of substitution less than 2.5; the latter polymers functioning to increase the water sensitivity of the adhesives which may be desired for some applications.
Other hydrophobic compatible polymers include elastomeric polymers such as styrene containing block copolymers, e.g., styrene-isoprene-styrene, epoxidized polyisoprene, styrene-butadiene-styrene, styrene-ethylene butylene-styrene, styrene-ethylene propylene styrene may also be present at levels up to about 30% by weight. Of these polymers, those based on styrene-isoprene-styrene are most preferred.
Among the applicable stabilizers or antioxidants which may be included herein are high molecular weight hindered phenols and multifunctional phenols such as sulfur and phosphorous-containing phenols. Representative hindered phenols include: 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxyphenyl) propionate; n-octadecyl 3,5-di-tert-butyl-4-hydroxyphenyl) propionate; 4,4xe2x80x2-methlenebis (2,6-di-tert-butylphenol); 4,4xe2x80x2-thiobis (6-tert-butyl-o-cresol); 2,6-di-tert-butylphenol; 6-(4-hydroxyphenoxy)-2,4-bis(n-octylthio)-1,3,5-triazine; di-n-octadecyl-3,5-di-tert-butyl-4-hydroxy-benzylphosphonate; 2-(n-octylthio)-ethyl 3,5-di-tert-butyl-4-hydroxybenzoate; and sorbitol hexa[3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate]. If used, the stabilizer is present in levels of about 0.05 to 3% by weight.
Other optional additives may be incorporated into the hot melt compositions in order to modify certain properties thereof. Among these additives may be included colorants such as titanium dioxide; and fillers such as talc and clay, etc.
Therefore in one embodiment, a hot melt adhesive composition in accordance with the present invention comprises (a) 20 to 80% by weight of a sulfonated polyester; (b) 0 to 35% by weight of a compatible tackifier; (c) 5 to 40% by weight of at least one crystalline material selected from the group consisting of a compatible crystalline wax diluent and a crystalline thermoplastic polymer; (d) 1-30% by weight of an anionic plasticizer; (e) 3 to 30% by weight of a pH adjusting agent, particularly an acidic plasticizer; (f) to 0.05 to 3% by weight of an indicating agent capable of changing color in response to changes in pH; and (g) 0 to 3% by weight of a stabilizer; wherein the total of (a)-(g) equals 100% by weight.
It will be recognized that the general formulation described above can be adapted to include a wide variety of hot melt adhesive compositions, the more precise formulations of which will vary depending upon the specific end use, as known to those skilled in the particular art.
The hot melt adhesive compositions of the invention may be formulated using techniques known in the art. An exemplary procedure for preparing an adhesive of the above embodiment involves placing approximately 40% of the total tackifying resin concentration with all the polymer, wax, plasticizers and stabilizers in a jacketed mixing kettle, preferably in a jacketed heavy duty mixer, which is equipped with rotors and thereupon raising the temperature to a range of from up to about 190xc2x0 C. After the resin has melted, the temperature is lowered to 150xc2x0 to 165xc2x0 C. Mixing and heating are continued until a smooth, homogeneous mass is obtained whereupon the remainder of the tackifying resin is thoroughly and uniformly admixed therewith.
As noted above, the sulfonated polyester containing hydrophilic hot melt adhesives of the invention will be formulated differently depending upon the particular end use. The resultant adhesives may be used in the assembly or construction of various disposable applications including, but not limited to, sanitary napkins, disposable diapers, hospital gowns, bed pads and the like. In particular, adhesives are useful for the construction of disposable articles using multi-line, spray, or slot-coating construction techniques wherein at least one flexible film substrate is bonded to at least one tissue, non-woven, polyolefin or other flexible polymeric film substrate.
With high levels of crystalline polymers, adhesives suitable as films or binder fibers can be prepared. Generally at least 15 and preferably 20 to 40% crystalline polymer is required for these applications. In contrast construction adhesives require a high degree of flexibility, but still need at least 5% of a crystalline polymer to avoid cold flow, preferably 5 to 10%.

Hot melt adhesives based on sulfonated polyesters comprising wetness indicator

National Starch and Chemical Investment Holding Corporation


Methods of treatment of cyanide-containing waste are provided. In particular, methods for treatment of spent potliner prior to landfill disposal are provided. These methods, which involve treatment of the waste with a mixture containing an aqueous oxidizing solution containing an agent, such as a metal chloride, that increases the oxidation potential of the solution, can be performed at ambient temperature and pressure.

The Hall-Heroult process for the production of metallic aluminum dates from the 19th century. Many refinements to the process have been made, but processes that use the basic Hall-Heroult process remain the most common processes for aluminum production throughout the world. In these processes, the bottom and internal walls of a cathode of an aluminum pot are formed with a liner of carbon blocks joined by conductive carbonaceous binder and wrapped with refractory firebricks and insulating bricks. The resulting combination is referred to as xe2x80x9cpotliner.xe2x80x9d The insulating bricks and firebricks are composed of material such as silica and alumina (aluminum oxide).
During the production of aluminum, the aluminum reduction pot is filled with a bath of alumina and molten salts. Over the three to seven year life span of an aluminum reduction pot, bath salts migrate into the potliner, thereby resulting in the deterioration and eventual failure of the aluminum cell as a cathode. During its lifespan, a cathodic potliner may absorb its own weight in bath salt materials. The failed potliner material is referred to herein as xe2x80x9cspent potliner.xe2x80x9d
When an aluminum reduction cell is taken out of service, the spent potliner is cooled and fractured to facilitate handling and disposal. The fractured spent potliner is a nonhomogeneous material that contains carbon, silica and/or alumina from the insulating brick and firebricks, aluminum, significant quantities of sodium salts, aluminum salts and oxides, fluoride salts and traces of cyanides. On the average, a large aluminum smelter with a production capacity of 175,000 tons of aluminum per year will produce about 6,000-12,000 tons of spent potliner per year. The quantity of spent potliner generated annually in the United States exceeds approximately 230,000 tons per year.
Because of its cyanide content, its high concentrations of other constituent compounds, and the high volumes of spent potliner produced, spent potliner presents a potential environmental hazard and a major burden for aluminum producers, who remain ultimately liable for the proper disposition of Spent Potliner.
The first cut of the spent potliner contains the carbon portion of the materials contained inside the two-electrode reduction cell. The second cut, which the U.S. Environmental Protection Agency (EPA) does not list as a hazardous waste, includes the other materials contained in the potliner. The spent first cut of the potliner (hereinafter referred to as xe2x80x9cSpent Potlinerxe2x80x9d) has long been listed as a hazardous waste by the EPA and state environmental authorities based on toxicity and the presence of cyanide complexes. Regulations require that treatment of listed Spent Potliner to reduce cyanide concentrations and other constituent compounds before it can be placed in a landfill disposal site.
There are a variety of approaches for reducing the potential toxicities of Spent Potliner. One technique includes combustion or incineration of the Spent Potliner (see, e.g., U.S. Pat. Nos. 4,735,784; 4,927,459; 5,024,822; 5,164,174; 5,222,448 and 5,286,274). Most of these processes result in a product in the form of glassy slag material that still contains some hazardous materials.
Other process include chemical treatment (see, e.g., U.S. Pat. No. 4,113,831). In these processes, the initial Spent Potliner constituents are replaced with compounds that are less toxic, but which still include hazardous components at levels above those established by various environmental authorities.
Another treatment involves pyrohydrolysis the Spent Potliner in conjunction with the introduction of water to create an off-gas containing fluoride materials present in the Spent Potliner (see, e.g., U.S. Pat. No. 4,113,832). Such pyrohydrolysis techniques may also be used in with fluidized bed reactors (see, e.g., U.S. Pat. Nos. 4,158,701 and 4,160,808). These processes tend to produce large volumes of waste material that must be disposed in landfills and that may contain non-leachable hazardous waste.
Other methods for treating cyanide-containing wastes, such as Spent Potliner, can be divided into two groups: methods that destroy cyanide by breaking the ion to form simpler, non-hazardous compounds (such as carbon dioxide and nitrogen gas) by an oxidation or electrolytic decomposition; and methods that reduce the volume of cyanide waste by an evaporation, reverse osmosis or ion exchange.
Oxidation has been used in the destruction of cyanide to form carbon dioxide and nitrogen. The process generally is effective in destroying free cyanide and some cyanide complexes. Oxidation of cyanide wastes is achieved through the addition of chlorine under alkaline pH conditions (alkaline chlorination), such as through the addition of sodium hypochlorite or through the addition of ozone (ozonation) or hydrogen peroxide (peroxidation) at elevated temperature and pressure. These processes involve handling large volumes of toxic and/or corrosive chemicals and generally are not effective on wastes that contain complexed cyanides, such as the cyanides present in Spent Potliner generated by many aluminum companies.
Electrolytic decomposition involves passing an electric current through the cyanide solution to break the cyanide ion. The process is effective in the destruction of free and complexed forms of cyanide. Electrolytic decomposition, however, is a very expensive process because of the large amounts of electrical energy consumed and is applicable only where the cyanide concentrations are at a relatively high level. High capital equipment costs are also associated with the process.
Hence, there is still a need to develop methods for treatment of Spent Potliner to produce waste acceptable for disposal in a landfill. Accordingly, it is an object herein to provide methods for treatment of cyanide-containing wastes, particularly, Spent Potliner material from aluminum reduction cells, for disposal in a landfill.
It is another object herein to provide methods for the chemical destruction of cyanide (free or as a metal complex), such as that present in Spent Potliner, for disposal in landfills. It is another object herein to provide methods for the destruction of cyanide (free or as a metal complex) that is safe and cost effective.
Provided herein are methods for treatment of cyanide-containing hazardous waste, particularly metal-containing waste, such as that generated by the aluminum industry. In particular, methods for treatment of Spent Potliner for destruction of cyanide are provided. The methods provided herein involve treating the waste, such as Spent Potliner, with an aqueous oxidizing solution that contains a sufficient amount of oxidizing agent to reduce the cyanide concentrations. The cyanide concentrations can be lowered to levels required by the EPA for disposal. Hence the methods provided herein lower levels to at about 590 parts per million (ppm) total cyanide or less and 30 ppm amenable cyanide or less, and preferably to 500 ppm total cyanide or less. These methods advantageously can be performed at ambient temperature and pressure. Typically the reaction is complete within an hour.
The time for completion will vary as function of cyanide concentration, forms of cyanide present and reagent concentrations. The precise conditions and concentration reagents for particular types of waste and sources thereof may be readily determined empirically based upon the instant disclosure.
The aqueous oxidizing solution preferably contains a hypochlorite, a peroxide or a permanganate, and more preferably the aqueous oxidizing solution contains calcium hypochlorite or sodium hypochlorite. The effectiveness of the oxidizing solution is enhanced by adding an agent that increases the oxidation/reduction potential (ORP) of the oxidizing solution to enhance cyanide destruction.
The concentration or amount of oxidizing agent used depends upon the initial concentration of cyanide in the waste, and can be determined empirically or adjusted during the reaction. For example, the progress of a reaction can be assessed by monitoring the oxidation potential of a mixture of the waste, such as Spent Potliner, and aqueous oxidizing solution. The desired oxidation potential of a aqueous oxidizing waste mixture following the treatment of, for example Spent Potliner, is preferably less than about 400 millivolts (mv). If there is remaining cyanide above the desired level, additional aqueous oxidizing solution is added.
Agents that enhance the oxidation potential (ORP) of the waste for destruction of cyanide in the waste, such as crushed Spent Potliner, include, but are not limited to, chlorine gas that is bubbled into the solution, hydrogen peroxide, ozone in solution, magnesium chloride, calcium chloride, potassium chloride and also potassium permanganate. Magnesium chloride, calcium chloride and potassium chloride are preferred; magnesium chloride is most preferred. If permanganate is used, the pH of the solution must be monitored to ensure that it remains alkaline.
A metal carbonate or other buffering agent is optionally added for treatment of certain cyanide-containing waste. The optional metal carbonate is selected from alkali metal carbonates and alkaline earth metal carbonates. It has been found that for treatment of Spent Potliner, addition of a metal carbonate is not necessary.
In an embodiment of the methods provided herein for the treatment of the waste, such as Spent Potliner, a metal chloride is also included in the aqueous oxidizing solution. In particular, the waste, such as the Spent Potliner is contacted with a mixture containing the aqueous oxidizing solution and the metal chloride or other agent that increases the oxidation potential of the aqueous oxidizing solution in amounts and for a time sufficient to reduce the cyanide levels, preferably to EPA required levels, particularly lower than 590 ppM total cyanide. As noted, the reaction can be performed at ambient temperature and pressure. In addition, the waste, such as the Spent Potliner is preferably crushed, to preferably fine powder containing pieces of a size from about 0.25 inch minus (i.e., less than xc2xc inch) to about 1.25 inch minus, prior to treatment.
The metal chloride is selected from alkali metal chlorides and alkaline earth metal chlorides. The preferred metal chloride is magnesium chloride, and preferably the aqueous oxidizing solution contains magnesium or calcium ions.
A. Definitions
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art to which this invention belongs. All patents, patent applications and publications referred to herein are incorporated by reference in their entirety.
As used herein, xe2x80x9cpotlinerxe2x80x9d refers to the carbonaceous material cell lining and insulating lining which form the bath-holding cavities of the aluminum reduction smelting cells.
As used herein, xe2x80x9cSpent Potlinerxe2x80x9d refers to the aged and degraded carbonaceous material cell lining and insulating lining that is removed from the smelting cell because it has become intercalated with cyanides, fluorides, polynuclear aromatics (PNA""s) or heavy metals (such as lead, beryllium, and cadmium), and is listed as a hazardous waste by the EPA. When capitalized and written as xe2x80x9cSpent Potlinerxe2x80x9d, it is the EPA listed material that is contemplated.
As used herein, xe2x80x9ccyanidexe2x80x9d refers to free cyanide (CNxe2x88x92, HCN) and complexed cyanides. Cyanides are determined by standard methods. Cyanide may be present in several forms in waste and is classified according to the difficulty of the digestion step in the colorimetric determination method prescribed by the EPA:
1. Free cyanide CNxe2x88x92, HCN;
2. Simple cyanide compounds, including the readily soluble NaCN, KCN, Ca(CN)2, Hg(CN)2, relatively insoluble, including ZN(CN)2, CuCN, Ni(CN)2 and AgCN;
3. Weak metal-cyanides, including Zn(CN)42xe2x88x92, Cd(CN)3xe2x88x92 and Cd(CN)42xe2x88x92;
4. Moderately strong cyanides, including Cu(CN)2xe2x88x92, Cu(CN)3xe2x88x92, Ni(CN)42xe2x88x92 and Ag(CN)2xe2x88x92; and
5. Strong metal-cyanides, such as Fe(CN)63xe2x88x92, Fe(CN)64xe2x88x92, Co(CN)64xe2x88x92, Au(CN)2xe2x88x92 and Hg(CN)42xe2x88x92.
Cyanides in group 5 do not appear to be digested in the methods for cyanide determination prescribed by the EPA.
As used herein, xe2x80x9camenable cyanidexe2x80x9d refer to the portion of the cyanides present in waste that can be chlorinated and destroyed by bleach (includes 1-4 above).
As used herein, xe2x80x9cmetal carbonatexe2x80x9d refers to either alkali metal (Li, Na, K, Rb, Cs, Fr) or to alkaline earth metal (Be, Mg, Ca, Sr, Ba, Ra) carbonates.
As used herein, xe2x80x9cmetal chloridexe2x80x9d refers to either alkali metal (Li, Na, K, Rb, Cs, Fr) or to alkaline earth metal (Be, Mg, Ca, Sr, Ba, Ra) chlorides.
As used herein, xe2x80x9can aqueous solution of metal chloridexe2x80x9d refers to a solution comprising a metal chloride and water.
As used herein, xe2x80x9cmetal hypochloritexe2x80x9d refers to either alkali metal (Li, Na, K, Rb, Cs, Fr) or to alkaline earth metal (Be, Mg, Ca, Sr, Ba, Ra) hypochlorites. Alkali metal hypochlorites include sodium hypochlorite (NaOCl) and alkali earth metal hypochlorites include calcium hypochlorite (Ca(OCl)2.
As used herein, xe2x80x9cambient temperature and pressurexe2x80x9d refers to temperature and pressure of the environment where Spent Potliner is treated. Typically, such temperature ranges from about 0xc2x0 C. to about 40xc2x0 C. and ambient pressure is about 1 atm.
As used herein, xe2x80x9can oxidizing agentxe2x80x9d refers to a substance that oxidizes something especially chemically as by accepting electrons.
As used herein, xe2x80x9can aqueous oxidizing solutionxe2x80x9d refers to any solution containing an oxidizing agent and water.
As used herein, xe2x80x9ca reducing agentxe2x80x9d refers to a substance that reduces a chemical compound usually by donating electrons.
As used herein, xe2x80x9coxidation potentialxe2x80x9d refers to the tendency of an element, metal or non-metal, or an ion, to be oxidized, or to give up electrons.
As used herein, xe2x80x9creduction potentialxe2x80x9d refers to the tendency of an element, metal or non-metal, or an ion, to be reduced, or to accept electrons.
As used herein, xe2x80x9coxidation-reduction potentialxe2x80x9d refers to a measure of the oxidizing or reducing strength of a solution. An oxidizing agent has a potential to acquire electrons and become reduced while a reducing agent has a potential to donate electrons and become oxidized.
As used herein, an agent that enhances the oxidation potential of the oxidizing solution is an agent that increases the oxidization strength of the oxidizing solution. Any such agent that achieves this result is contemplated herein; such agents include, but are not limited to, bubbled chlorine gas in the solution, hydrogen peroxide, ozone in the solution, magnesium chloride, calcium chloride, potassium chloride, and potassium permanganate.
As used herein, xe2x80x9can oxidation-reduction reactionxe2x80x9d refers to when electrons are transformed from one species to another in a chemical reaction. Oxidation and reduction reactions occur together, the electrons generated by a reduction reaction must be acquired by an oxidation reaction. The electron transfer between the two species continues until an equilibrium is reached.
As used herein, xe2x80x9cmeasuring the oxidation potentialxe2x80x9d refers to any electrochemical method of determining the tendency of an element, metal or non-metal, or an ion, to be oxidized, or to give up electrons.
As used herein, xe2x80x9cEPA landfill waste disposal standardsxe2x80x9d refers to the standards promulgated by the EPA, and can be readily accessed (see, e.g., 40 C.F.R. Parts 268 and 271, Land Disposal Restrictions; Treatment Standards for Spent Potliners From Primary Aluminum Reduction (K088); Final Rule. Maximum cyanide concentration permitted in waste from sources, such as Spent Potliner, for disposal in landfills is 590 ppm total cyanide and 30 ppm amenable cyanide. The methods herein reduce concentrations to these levels.
Cyanide Wastes
Cyanide is used industrially in the form of sodium cyanide (NaCN) and hydrocyanic acid (HCN). These compounds are used as raw materials or as processing chemicals in various industrial operations, such as in mining, photographic processing, synthetic fiber manufacturing, steel processing, industrial gas scrubbing and electroplating. The major source of waste cyanide is produced by the electroplating industry, where cyanide is used in plating baths to hold metal ions such as zinc and cadmium in solution. The methods provided herein may be used to treat cyanide-containing waste from any source, including the electroplating industry.
Cyanide is present in Spent Potliners and in industrial waste streams in either of two forms: free cyanide (CNxe2x88x92), and complexed cyanide (such as FeCNxe2x88x92). Free cyanide in solution is quite amenable to destruction by oxidation methods. Destruction of complexed forms of cyanide (i.e., xe2x80x9ccyanide complexesxe2x80x9d) in solution by means of oxidation is highly dependent on the complexing ion associated with the cyanide radical. The relative stability among cyanide complexes varies depending on the complexing ion that is bound to the cyanide radical.
The preferred embodiments herein are directed to the destruction of cyanide present in Spent Potliner, and practice of the methods herein is exemplified with Spent Potliner.
Spent Potliners as Hazardous Waste
Spent Potliners from primary aluminum reduction (40 CFR 261.32, Industry and EPA hazardous waste No. K088) is generated by the aluminum manufacturing industry. Aluminum production occurs in four distinct steps: (1) mining of bauxite ores; (2) refining of bauxite to produce alumina; (3) reduction of alumina to aluminum metal; and (4) casting of the molten aluminum. Bauxite is refined by dissolving alumina (alumina oxide) in a molten cryolite bath. Next, alumina is reduced to alumina metal. This reduction process requires high purity aluminum oxide, carbon, electric power, and an electrolytic cell. An electric current reduces the alumina to aluminum metal in electrolytic cells, called pots. These pots contain a steel shell lined with brick with an inner lining of carbon. During the pot""s service the liner is degraded and broken down. Upon failure of a liner in a pot, the cell is emptied, cooled, and the lining is removed. In 1980, the EPA originally listed Spent Potliners as a RCRA hazardous waste and assigned the hazardous waste number K088 (see, 45 FR 47832). Later in 1980, the EPA determined that a Congressional act excluded Spent Potliner from being listed as a hazardous waste (see, 45 FR 76619). In 1988, the EPA listed Spent Potliner as a hazardous waste, effective in 1989 (see, 53 FR 35412).
The EPA has promulgated treatment standards for Spent Potliners from primary aluminum reduction (EPA hazardous waste: K088) under its Land Disposal Restrictions (LDR) program. The purpose of the LDR program, authorized by the Resource Conversation and Recovery Act of 1976, as amended by the Hazardous and Solid Waste Amendments of 1984, is to minimize threats to human health and the environment due to land disposal of hazardous wastes. As a result, Spent Potliners are prohibited from land disposal unless the wastes have been treated in compliance with the numerical standards contained in this rule. These treatment standards are necessary to minimize threats to human health and the environment from exposure to hazardous constituents which may potentially leach from landfills to groundwater.
Entities potentially affected by this action are generators of spent aluminum potliner from primary aluminum reduction, or entities that treat, store, transport, or dispose of these wastes.
Chemistry
The methods provided herein are useful for effectively and efficiently destroying or oxidizing cyanide (free cyanide and cyanide complexes) in cyanide-containing waste, such as Spent Potliner. The methods contact the waste with an oxidizing agent. In particular embodiments, the waste is treated with a mixture of an oxidizing agent and a metal chloride (or other agent that increases the oxidation potential of the mixture) in an aqueous solution. The combination of these two reagents acts to destroy or oxidize cyanide, and result in a mixture with acceptable levels of cyanide for landfill disposal. The reactions can be performed in air at ambient temperature and pressure, to destroy either free or complexed cyanide.
The chemistry described herein is useful for treatment of waste in settings apart from destroying cyanides in Spent Potliner. The preferred embodiments of the methods described herein are exemplified with reference to destroying cyanides present in Spent Potliner.
The combination of an oxidizing agent such as calcium hypochlorite (Ca(OCl)2), potassium hypochlorite (KOCl) and sodium hypochlorite (NaOCl), and a metal chloride such as magnesium chloride (MgCl2) or calcium chloride (CaCl)2), in an aqueous solution, generates among other products, carbon dioxide (CO2). For some wastes, if needed, a buffering agent, such as a metal carbonate, particularly calcium or magnesium carbonate (CaCO3), is optionally added to avoid production of undesirable volatiles and gases. Generally such agent is not needed.
The combination of these reagents causes the cyanides first to partition into the aqueous phase and then to oxidize. When calcium hypochlorite or sodium hypochlorite is used alone, cyanides, especially when the cyanide is bound with iron or copper, are not effectively destroyed because the reaction rate is slow or non-existent. Addition of magnesium chloride enhances this reaction substantially. Without being bound by any theory, it appears that magnesium chloride appears to accelerate the reaction that destroys the cyanide. Thus, the combination of magnesium chloride and calcium or sodium hypochlorite in an aqueous solution provides an effective means for the destruction of cyanides in wastes, such as Spent Potliner.
The aqueous oxidizing solution contains an oxidizing agent that is present in sufficient amounts to oxidize or destroy cyanide. Oxidizing agents that are useful to destroy cyanide include but are not limited to: metal hypochlorites including alkali metal hypochlorites such as sodium hypochlorite (NaOCl) and potassium hypochlorite, and alkaline earth metal hypochlorites such as calcium hypochlorite (Ca(OCl)2) and magnesium hypochlorite (Mg(OCl)2); halogens such as fluorine, chlorine, bromine and iodine; permanganates such as potassium permanganate (KMnO4); peroxides such as hydrogen peroxide; and peroxyacids such as peracetic acid.
Metal chlorides include, but are not limited to: alkali metal (Li, Na, K, Rb, Cs, Fr) chlorides, such as sodium chloride (NaCl) or alkaline earth metal (Be, Mg, Ca, Sr, Ba, Ra) chlorides. Magnesium chloride (MgCl2), potassium chloride, and calcium chloride (CaCl2) are presently preferred; magnesium chloride (MgCl2) is most preferred.
Metal carbonates include, but are not limited to: alkali metal (Li, Na, K, Rb, Cs, Fr) carbonates, such as sodium carbonate (Na2CO3), or to alkaline earth metal (Be, Mg, Ca, Sr, Ba, Ra) carbonates, such as calcium carbonate (Ca(CO3).
An advantage of the present methods is the use of these inexpensive, safe and readily available reagents for the destruction of cyanide in Spent Potliners.
Another advantage of the present methods, includes the ability to monitor the levels of cyanide destruction in the treated Spent Potliner waste solution. Monitoring is accomplished by measuring the oxidation potential of the waste solution, using standard electrochemical methods including, but not limited to, potentiometric methods, colorimetric methods. Monitoring and adding additional oxidizing agent, metal chloride allow for the reduction of cyanide levels present in cyanide-containing waste, such as Spent Potliner, with minimal volumes of treated Spent Potliner waste.
For convenience and efficiency of the methods, when applied to Spent Potliner, the Spent Potliner is optionally crushed, such as in a crusher or a pulverizer, to give particles, preferably of a size from about 0.25 inch minus to about 1.25 inch minus prior to treatment.
Without being bound by any theory, the following reactions are believed to be involved in the methods, referred to as alkaline chlorination, provided herein.
Decomposition/Oxidation of the Cyanide Ion
Oxidation and decomposition of free cyanide occurs in two stages. The cyanide is first oxidized to cyanates (CNOxe2x88x92), which is then further oxidized to carbon dioxide, nitrogen gas and chlorides. Oxidation and decomposition of complexed cyanide occurs only with some species, such as the species 2-4 described above. These oxidation reactions are slower than those involving free cyanides. Metal hydroxides in addition to the bicarbonates and nitrogen gas are produced.
Other combined forms, particularly the strong metal-cyanides, such as Fe(CN)63xe2x88x92, Fe(CN)64xe2x88x92, Co(CN)64xe2x88x92, Au(CN)2xe2x88x92 and Hg(CN)42xe2x88x92, are not affected by chlorine or hypochlorite at room temperature since these forms are already in an oxidized state. These forms may not be measured in the EPA methods for amenable cyanide determination, and, hence do not contribute to the measure amenable cyanide levels.
First Reaction Stage
In the first stage, cyanide is oxidized to cyanogen chloride in the presence of hypochlorite ion:
Hypochlorite: OClxe2x88x92+NaCN+H2Oxe2x86x92CNCl+1Na++20Hxe2x88x92
These reactions occur instantaneously and are independent of pH. By controlling the pH to above 8, preferably 10 to 11, CNCl desirously is converted to a less volatile more stable compound:
CNCl+2OHxe2x88x92xe2x86x92CNOxe2x88x92+Clxe2x88x92+H2O
Hence the overall reaction governing transformation of free cyanide to cyanates is:
Hypochlorite: OClxe2x88x92+CNxe2x88x92xe2x86x92CNOxe2x88x92+Clxe2x88x92
Addition of CaCO3, such as by performing these reactions in the presence caustic soda or lime, maintains the desired pH.
Second Reaction Stage
In the second reaction stage, cyanates are further oxidized to ammonium and sodium carbonates in the presence of excess hypochlorite, which catalyze the reactions:
Hypochlorite: 4CNOxe2x88x92+3OClxe2x88x92+8H2Oxe2x86x923OClxe2x88x92+2(NH4)2CO3+2CO3xe2x88x92
The resulting ammonium carbonate is rapidly oxidized to form nitrogen gas and the carbonates are converted to bicarbonates:
Hypochlorite: 2(NH4)2CO3+6OClxe2x88x92+2CO3xe2x88x92xe2x86x924HCO3xe2x88x92+2N2+6Cxe2x88x92+6H20
Small amounts of nitrous oxide and volatile nitrogen trichloride also can be formed in these reactions.
The overall reaction is as follows:
Hypochlorite: 2CNOxe2x88x92+3OClxe2x88x92+H2Oxe2x86x922HCO3xe2x88x92+N2+3Clxe2x88x92
Methods of Treatment of Spent Potliner
In a preferred embodiment, crushed Spent Potliner (about 0.25 inch minus) is treated with a mixture of sodium hypochlorite and magnesium chloride. This same mixture of reagents is used to treat the mixture of all of the other generations of potliner. The quantity of the reagents are adjusted depending upon the initial concentrations of cyanide in the Spent Potliner.
In a further embodiment, the metal chloride is about 35% aqueous calcium chloride, and the ratio of the about 35% aqueous calcium chloride to Spent Potliner is from about 5 to about 120 gallons per ton.
In a further embodiment, the ratio of the about 35% aqueous magnesium chloride or calcium chloride to Spent Potliner is from about 10 to about 100 gallons per ton.
In a further embodiment, the aqueous oxidizing solution is about 13% aqueous sodium hypochlorite, and the ratio of the about 13% aqueous sodium hypochlorite to Spent Potliner is from about 20 to about 240 gallons per ton.
In a further embodiment, the ratio of the about 13% aqueous sodium hypochlorite to Spent Potliner is from about 30 to about 200 gallons per ton.
In another embodiment, cyanide-containing waste, such as Spent Potliner, is reacted with a metal chloride, such as calcium chloride, a hypochloride and a metal carbonate, whereby the cyanide is destroyed resulting in EPA-acceptable levels.
The methods provided herein are preferably performed at ambient temperature and pressure and can be performed in an open environment or in a sealed reactor, at ambient or elevated temperature and/or pressure.
The following example is included for illustrative purposes only and are not intended to limit the scope of the invention.

Methods of destruction of cyanide in cyanide-containing waste